The Big Nugget is the name of an asteroid that passed extremely close to Arbre, and was originally feared might impact the planet.
The Big Nugget was discovered in A.R. 1107, almost a decade before it was projected at hitting Arbre. The global danger prompted the Saecular Power at that time to convene a Convox to develop methods to deflect the asteroid. Although the specific means by which they intended to alter the asteroid's orbit are not given in the novel, the Convox did develop spacecraft and hardened spacesuits for a manned expedition to the Big Nugget. From the timeline presented in the begining of the book this flight may have occurred in A.R. 1115.
The research done into this space technology was of extreme importance following the discovery of the Daban Urnud in orbit around Arbre in A.R. 3688. The technical documentation from the Big Nugget Convox survived the Third Sack (A.R. 2787 - 2856) due to heroic efforts by some Fraas and Suurs who carried for decades until the Mathic System was reestablished. The information was stored at the Concent of Saunt Rab, until it was put into use in the Thirty Fifth century.
In many cases handwritten notes, over 2500 years old, were used to recreate the space technology. The technical information was such that the hardened spacesuits used by Cell 317 to infiltrate the Daban Urnud were able to be constructed in less that a year.
Jesry specifically mentions the development of new hardened spacesuits based on the books and notes of the Big Nugget Convox. Unmanned space technology clearly existed in the world of Fraa Erasmas prior to the discovery of the Daban Urnud. References are made to Arbran satellites in polar orbit, that rocket launches are common, and the use of global positioning satellites with cartabulas.